I have VERY straight hair and tried for years to have some sort of curl in it, but nothing worked or it was straight again after an hour.
A few months ago I bought the MiraCurl from BabylissPro. It's so easy to use, very fast and it gives me amazing curls.
Before using my MiraCurl I use the anti gravity spray from Kevin Murphy.
Thanks to this spray my curls stay even longer.
At the end I always use a special comb for curls, it makes it look more natural.
Now I have this amazing curls for 2-3 days (probably longer but I have to wash my hair :D)